An attempt by a US diplomat to recruit a Russian agent for the Central Intelligence Agency is an impediment to efforts to improve US-Russian relations, President Vladimir Putin's spokesman said.

In the first Kremlin comment on the detention and expulsion of the diplomat, spokesman Dmitry Peskov told Itar-Tass news agency that the incident was regretful. But he did not threaten any further action over the incident.

The Russia Today website has published a photograph of what it claims is a letter, found in a US diplomat's possession, that was to be used to recruit a Russian as an intelligence officer.

The website also provided the following transcript of part of the letter:

Dear Friend,

This is a down-payment from someone who is very impressed with your professionalism and who would greatly appreciate your cooperation in the future. Your security means a lot to us. This is why we chose this way of contacting you. We will continue to make sure our correspondence remains safe and secret.

We are ready to offer you $100,000 to discuss your experience, expertise and cooperation. The reward may be much greater if you are willing to answer specific questions. In additin to that, we can offer up to $1 million a year for long-term cooperation ...

It goes on to describe how the recipient should open a Gmail account at an Internet cafe, instructing the recipient to expect an email response in "exactly one week".